BOOK AND LABEL CLASS IMPLEMENTATION

[henrycode460]

This branch contains the followings:

• A book and label class.
• Both the book and label class contains can_be_archive and add_item methods respectively
• The is a one-to-many relationship between the label and the item class.
• The book call inherent publish_date from the item class to add the date to the publication of the book
• There are unit testson all the methods of the book and label classes.
• Input accepted for a user to store books and labels are saved in a JSON file.
• There is a schema to display the attribute of the book and label class according to the UML diagram given.